Synthetic layered silicate nanolayers

Abstract

Nanolayered layered silicate materials of octahedrally arranged units with divalent metal ions at centers of the units covalently linked above and below to tetrahedrally arranged oxygen and hydroxyl units with silicon atoms. The silicate materials contain silanol groups which are reactive to form derivative compositions useful for water purification to remove heavy meal cations.

1. A synthetically derived organofunctional silicate composition consisting of elementary nanolayers formed from a central sheet of octahedrally arranged oxygen units with divalent metal cations occupying positions at the centers of the octahedral units to provide an octahedral sheet, said octahedral sheets being covalently linked above and below by sheets of tetrahedrally arranged oxygen and hydroxyl units with silicon atoms occupying positions in the center of each tetrahedrally arranged oxygens (the tetrahedral sheets), wherein dimensions of the elementary nanolayers vary from about 1 to 200 nanometers, the elementary nanolayers being aggregated into particles less than about 2 micrometers in dimension, the number of stacked elementary three-sheet nanolayers varying from predominately one nanolayer as unstacked nanolayers to no more than five nanolayers, while in the octahedral sheet up to 16 percent of the octahedrally arranged oxygen units are vacant and while in the tetrahedral silicate sheets at least 5 percent and up to 35 percent of the silicon atoms are linked to hydroxyl groups, and wherein surface silanol groups on the tetrahedral sheet of the nanolayers have been converted to organosilyl groups by reaction with an organosilane grafting reagent. 
     
     
       2. The compositions of  claim 1 , wherein the organosilyl groups comprise oxygen, nitrogen, halogen, sulfur, phosphorous, boron and combinations thereof covalently bonded to carbon. 
     
     
       3. The silicate composition according to  claims 1  or  2 , wherein in the octahedral sheet the divalent metal cations are selected from the group consisting of magnesium, zinc, nickel, cobalt, iron, manganese, and combinations thereof. 
     
     
       4. The compositions of  claims 1  or  2  characterized by the nanolayers having a deficiency of positive charge which is comprised of exchangeable divalent cations on surfaces of the nanolayers. 
     
     
       5. The compositions of  claim 4 , wherein the exchangeable divalent cations on the surface of the nanolayers are replaced by an inorganic cation, an organic onium ion, or a metal complex cation.